Inorganic boron compounds have been used as wood preservatives and fire retardants for many years. The basic materials, boric acid and borax, are readily available, inexpensive and relatively harmless to humans, and their toxicity to fungi, termites, and wood-destroying insects has been clearly established. At higher levels of treatment, the borates are also effective as fire-retardants for lumber and other wood products. However, since the commonly used borates are readily soluble in water, their use has been restricted to applications where leaching is not likely to occur, such as by rain water or soil moisture. In order to alleviate this limitation, various means for insolubilizing or fixing the borate in the wood have been proposed. For example, Du Fresne et al., U.S. Pat. No. 3,306,765, shows impregnation of wood with a mixture of sodium silicate and borax and then treatment with carbon dioxide under pressure to fix the fireproofing agents against leaching. See also USSR Patent 283,546 (Chemical Abstracts 75,75338) and Japanese Kokai Tokkyo Koho 62,275,703 (Chemical Abstracts 108, 169476) which propose treating with a soluble borate-containing preservative and then altering the pH such as with ammonia to precipitate insoluble preservatives in the wood.
Water-soluble zirconium salts are known and have various uses such as for insolubilizing starch binders used in paper coating compositions and to impart thixotropy to dispersions of polymers such as emulsion paints. See Phillips U.S. Pat. No. 4,097,430. Water-insoluble salts of metals such as copper, mercury and nickel are known to be fungicidal and can be solubilized by mixing with zirconyl acetate in acetic acid solution or with zirconyl ammonium carbonate solutions to provide compositions for rendering cotton fabric rot-resistant. See Conner, U.S. Pat. Nos. 3,183,118 and 3,291,635. Copper borate and phenyl mercury borate are among the metal salts that may be used. For example, cotton fabric can be treated with solubilized copper borate and then cured, such as by heating at 145.degree. C., to convert the soluble form to an insoluble form. Subsequently, Conner et al. substituted copper carbonate for copper borate. See Textile Chemist and Colorist, April 1978, and see Sherif et al. U.S. Pat. No. 4,274,972, which claims a process for preparing an improved dilute aqueous copper zirconium ammonium carbonate solution, having enhanced resistance to gelation.
Japanese Kokai Tokkyo Koho 58,164,673 (1983)(Chemical Abstracts, Vol. 100, 54052) describes preparation of a fireproofing agent from a mixture of acidified shellfish fossils and siliceous soil with a solution of boric acid, borax and zirconium silicate.
Although a simple zirconium borate has not been well-defined, anhydrous and hydrated zirconium borates are reviewed in Supplement to Mellor's Comprehensive Treatise on Inorganic and Theoretical Chemistry, Volume V, Part A, Pages 618-619 (1980).